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Showing papers in "Sensors and Actuators A-physical in 2013"


Journal ArticleDOI
TL;DR: In this article, a microfluidic sensor is implemented from a single split-ring resonator (SRR), a fundamental building block of electromagnetic metamaterials, which is capable of sensing liquid flowing in the channel with a cross-sectional area as small as (0.001 λ 0 ) 2.
Abstract: A microfluidic sensor is implemented from a single split-ring resonator (SRR), a fundamental building block of electromagnetic metamaterials. At resonance, an SRR establishes an intense electric field confined within a deeply subwavelength region. Liquid flowing in a micro-channel laid on this region can alter the local field distribution and hence affect the SRR resonance behavior. Specifically, the resonance frequency and bandwidth are influenced by the complex dielectric permittivity of the liquid sample. The empirical relation between the sensor resonance and the sample permittivity can be established, and from this relation, the complex permittivity of liquid samples can be estimated. The technique is capable of sensing liquid flowing in the channel with a cross-sectional area as small as (0.001 λ 0 ) 2 , where λ 0 denotes the free-space wavelength of the wave excitation. This work motivates the use of SRR-based microfluidic sensors for identification, classification, and characterization of chemical and biochemical analytes.

348 citations


Journal ArticleDOI
TL;DR: In this paper, the authors define concise performance metrics and provide exact and approximate expressions for error sources including nonlinearity, drift and noise for position sensors with nanometer resolution, including resistive, piezoelectric and piezoresistive strain sensors.
Abstract: Position sensors with nanometer resolution are a key component of many precision imaging and fabrication machines. Since the sensor characteristics can define the linearity, resolution and speed of the machine, the sensor performance is a foremost consideration. The first goal of this article is to define concise performance metrics and to provide exact and approximate expressions for error sources including non-linearity, drift and noise. The second goal is to review current position sensor technologies and to compare their performance. The sensors considered include: resistive, piezoelectric and piezoresistive strain sensors; capacitive sensors; electrothermal sensors; eddy current sensors; linear variable displacement transformers; interferometers; and linear encoders.

324 citations


Journal ArticleDOI
TL;DR: The 9th International Workshop on Piezoelectric Materials and Applications in Actuators (IWPMA 2012) was successfully held on 22-25 April 2012 in Hirosaki, Japan as discussed by the authors.
Abstract: The 9th International Workshop on Piezoelectric Materials and Applications in Actuators (IWPMA 2012) was successfully held on 22–25 April 2012 in Hirosaki, Japan. The general chair was Prof. M.K. Kurosawa from the Tokyo Institute of Technology, Japan. In the past, Korea, Germany, Turkey, China, and USA have hosted the annual conference, but this was the first time for the annual IWPMA conference to be held in Japan. The IWPMA 2012 was organized as a joint symposium with JTTAS Smart Actuator/Sensor Study Committee and ICAT International Actuator Symposium. More than 150 people from the world (12 countries) participated and had fruitful discussions with 138 presentations including 11 invited talks. In addition to piezoelectric materials and piezoelectric actuators, the presentation topics were expanded to include solid-state actuators, energy harvesting, multifunctional materials, and other current important issues. It is our honor to pronounce that the “Sensors and Actuators A” journal has published this special issue on the IWPMA 2012 including the best 25 contributions. This issue covers the functional materials, such as piezoelectric and magnetostrictive materials, and their applications. However, for the innovative devices, various ideas concerning materials, mechanisms, designs, fabrication process, and control-systems are also required to be organically combined. From the view of this concept, we believe the published 25 papers can excite the researcher's intellectual curiosity concerning these issues and can serve as the driving force for further breakthroughs. Please enjoy the latest research results selected by our editor team. Finally, we appreciate all participants in the IWPMA 2012 and the devoted reviewers for the publication. We hope that the papers in this special issue will open up the next researches, which will be presented in the future IWPMA conferences.

268 citations


Journal ArticleDOI
TL;DR: In this article, the authors reported the hydrothermal synthesis at 95°C of Cu-doped ZnO low-dimensional rods for room-temperature (RT) sensing applications and enhanced sensor performances.
Abstract: Detection of chemicals and biological species is an important issue to human health and safety. In this paper, we report the hydrothermal synthesis at 95 °C of Cu-doped ZnO low-dimensional rods for room-temperature (RT) sensing applications and enhanced sensor performances. X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, Raman and photoluminescence are used to characterize the material properties. To demonstrate the suitability of the Cu-doped ZnO rods for gas sensor applications and for comparison with pure ZnO, we fabricated a double rod device using Focused Ion Beam. The responses of pure-ZnO and Cu-doped ZnO rods studied in exactly the same condition are reported. We found that Cu-ZnO sensors have enhanced RT sensitivity, faster response time, and good selectivity. Miniaturized Cu-ZnO rod-based sensors can serve as a good candidate for effective H2 detectors with low power consumption.

224 citations


Journal ArticleDOI
TL;DR: In this article, the authors used near-field electrospinning to fabricate polyvinylidene fluoride (PVDF) piezoelectric nanofibers mixed with multiwalled carbon nanotubes (MWCNT).
Abstract: This study reports the use of near-field electrospinning to fabricate polyvinylidene fluoride (PVDF) piezoelectric nanofibers mixed with multiwalled-carbon nanotubes (MWCNT). This study also investigates the mechanical strength and piezoelectric characteristics of a single PVDF/MWCNT nanofiber. The morphology and polarization intensity of piezoelectric fiber can be controlled by adjusting the traveling velocity of the X – Y stage, the DC voltage, and the gap between the needle and collection plate. The optimal parameters of the PVDF solution, such as the PVDF powder weight percentage and MWCNT content, were also determined. X-ray diffraction (XRD) analysis shows a high diffraction peak at 2 θ = 20.8° in the piezoelectric crystal β-phase structure. ANSYS finite element analysis (FEA) software with coupled field analysis was used to realize piezoelectric actuation behavior of the PVDF fibers. A nano-indentation test (NanoIndenter XP System, MTS co.) was used to investigate Young's modulus of the PVDF fiber. Finally, the fixed–fixed beam structures of PVDF composite fibers were tested using a DC voltage supply. Comparing the polarized fiber with non-polarized fibers, the measurement of the center displacements as a function of electric field was conducted and characterized.

189 citations


Journal ArticleDOI
TL;DR: In this paper, a piezoelectric polyvinylidene fluoride (PVDF) polymer-based sensor patch for simultaneous heartbeat and respiration detections is presented.
Abstract: This study reports a piezoelectric polyvinylidene fluoride (PVDF) polymer-based sensor patch for simultaneous heartbeat and respiration detections. The principle is based on the piezoelectric sensing mechanism to detect the pulsatile vibrations, and periodical deformations on the chest wall of human body during heartbeats and respirations, respectively. In this study, the sensor patch with a structurally curved PVDF film was designed, and fabricated. The role of the curved structure design to enhance detection signals, and the capability of the sensor to faithfully detect the heartbeats and respirations were experimentally evaluated. Results revealed that the design of curved structure of PVDF film was capable of increasing detection signal by 151% for the respiration measurements compared with its flat counterpart. Moreover, the sensor was proved to be able to generate the heartbeat and respiration signals which were in concordance with those based on a commercial electrocardiogram (ECG), and respiratory effort transducer, respectively. Finally, the heart rate and respiratory rate measured through the sensor patch were proved to have no statistical significance compared with the reference data obtained from the ECG, and respiratory effort transducer-based detections, respectively. As a whole, this study has developed a PVDF-based sensor patch which was capable of monitoring the heartbeats and respirations with high fidelity. Other distinctive features include its small size, light weight, ease of use, low cost, and portability. All these make it a promising sensing device to monitor heartbeats and respirations either in medical centers, or home care units.

147 citations


Journal ArticleDOI
TL;DR: In this article, the authors proposed a piezoelectric EH comprising a composite cantilever and a proof mass at the free end to overcome the low output power scavenged from low frequency vibrations, and limited effectiveness of harvesting mechanism in a narrow range near resonant frequency.
Abstract: The energy harvesters (EHs) using resonant mechanism have encountered two major issues: low output power scavenged from low frequency vibrations, and limited effectiveness of harvesting mechanism in a narrow range near resonant frequency. To overcome these issues, we have proposed a piezoelectric EH comprising a composite cantilever and a proof mass at the free end. The composite cantilever is formed by a piezoelectric bimorph and a polymer beam (soft spring) mechanically connected along the longitudinal direction. Comparing with the resonant frequency of 275 Hz of a standalone piezoelectric bimorph, the composite cantilever design enables the resonant frequency of the EH to be as low as 36 Hz. Moreover, this kind of EH is demonstrated to be 3.12 times and 1.32 times (at 0.1 g) more efficient at output power generation than a standalone piezoelectric bimorph and piezoelectric bimorph with a proof mass at the free end, respectively. With the aid of spring hardening effect, the operating bandwidth (BW) can be increased from 5 Hz to 16.4 Hz.

145 citations


Journal ArticleDOI
TL;DR: In this paper, a transparent film was used for heating, fabricated by employing a multi-walled carbon nanotube (MWCNT) sheet, which was made from a super-aligned MWCNT forest; the heater was fabricated by direct coating onto a glass substrate.
Abstract: This paper presents carbon nanotubes (CNTs) used as transparent heaters, which offer great advantages in miniaturization, high efficiency, low power consumption, and rapid response. Previously proposed transparent single-walled carbon nanotube (SWCNT) based heaters used to replace indium tin oxide (ITO) heaters were fabricated either by dielectrophoresis or the piece-wise alignment of read-out electronics around randomly dispersed CNTs. These methods require steps for purification, separation, and dispersion in a liquid or polymer in order to improve their electrical and optical properties. We studied a transparent film used for heating, fabricated by employing a multi-walled carbon nanotube (MWCNT) sheet. The sheet was made from a super-aligned MWCNT forest; the heater was fabricated by direct coating onto a glass substrate. The characteristics of the MWCNT sheet, i.e. a high transmittance of ∼90% and a sheet resistance of ∼756 Ω/sq, are comparable to previously reported SWCNT-based transparent films. These properties are directly applicable to applications such as window tinting and defrosters in production vehicles.

131 citations


Journal ArticleDOI
TL;DR: In this paper, the energy harvesting efficiency of electrospun poly(vinylidene fluoride), its copolymer vinylidene fluoride-trifluoroethylene and composites of the later with barium titanate ceramic fillers on interdigitated electrodes has been investigated.
Abstract: The energy harvesting efficiency of electrospun poly(vinylidene fluoride), its copolymer vinylidene fluoride-trifluoroethylene and composites of the later with barium titanate ceramic fillers on interdigitated electrodes has been investigated. Ceramic fillers of 500 (tetragonal), 100 (cubic) and 10 nm (cubic) have been used. Further, a study of the influence of the electrospinning processing parameters on the average size of the composites fibers has been performed. It is found that the best energy harvesting performance was obtained for pure poly(vinylidene fluoride) fibers, with power outputs up to 0.02 μW and 25 μW under low and high mechanical deformation. The copolymer and the composites show reduced power output mainly due to increased mechanical stiffness, the power output of the composites being better for the nonpiezoelectic smaller fillers. The obtained values, among the largest found in the literature, the easy processing and the low cost and robustness of the polymer, demonstrate the applicability of the developed system.

130 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present a long-term bias drift compensation algorithm for high quality factor (Q -factor) MEMS rate gyroscopes using real-time temperature self-sensing.
Abstract: We present a long-term bias drift compensation algorithm for high quality factor ( Q -factor) MEMS rate gyroscopes using real-time temperature self-sensing. This approach takes advantage of linear temperature dependence of the drive-mode resonant frequency for self-compensation of temperature-induced output drifts. The approach was validated using a vacuum packaged silicon Quadruple Mass Gyroscope (QMG), with signal-to-noise ratio (SNR) enhanced by isotopic Q -factors of 1.2 million. Owing to the high Q -factors, measured frequency resolution of 0.01 ppm provided a temperature self-sensing precision of 0.0004 °C, on par with the state-of-the-art MEMS resonant thermometers. The real-time self-compensation yielded a total bias error of 2°/h and a scale-factor error of 700 ppm over temperature range of 25–55 °C. The presented approach enabled repeatable long-term rate measurements required for MEMS gyrocompassing applications with a milliradian azimuth precision.

128 citations


Journal ArticleDOI
Jianping Li1, Hongwei Zhao1, Han Qu1, Tao Cui1, Lu Fu1, Hu Huang1, Ren Luquan1, Fan Zunqiang1 
TL;DR: In this article, a piezoelectric-driven stepping rotary actuator based on the inchworm motion is presented, which can realize large rotary ranges and high rotary speed with high accuracy.
Abstract: This paper presents a piezoelectric-driven stepping rotary actuator based on the inchworm motion. With the help of nine piezoelectric stacks and the flexure hinges, the designed actuator can realize large rotary ranges and high rotary speed with high accuracy. Three kinds of working units that compose the actuator are described and calculated: the clamping unit to hold the rotor, the adjusting unit to preload the piezoelectric stacks and the driving unit to produce the driving torque. To test the working performance, a prototype actuator was fabricated, and the experimental results indicate that the minimum stepping angle is 4.95 μrad when the driving voltage is 20 V and the frequency is 1 Hz, the maximum output torque is 93.1 N mm under the driving voltage of 100 V and the maximum velocity can be 6508.5 μrad/s when the frequency reaches 30 Hz. The experimental results verify that the proposed actuator can realize different stepping angles and rotation speeds with high accuracy under different driving voltages and frequencies.

Journal ArticleDOI
TL;DR: In this paper, the capability of metal and different oxide combinations to be used in surface plasmon resonance (SPR) based fiber-optic refractive index sensor by using wavelength interrogation technique is demonstrated.
Abstract: We have experimentally demonstrated the capability of metal and different oxide combinations to be used in surface plasmon resonance (SPR) based fibre-optic refractive index sensor by using wavelength interrogation technique. The analysis of the sensor response is carried out using multilayered structure and geometrical optics. The configuration contains copper as a SPR active metallic layer covered by one of the three oxide layers TiO 2 , SiO 2 , and SnO 2 . The thickness of the copper layer is optimized to achieve the most pronounced dip at the resonance condition. The maximum sensitivity is obtained for TiO 2 film. Further, increase in the thickness of the TiO 2 layer increases the sensitivity of the sensor. The trend of sensitivity obtained by experimental results match qualitatively with the theoretical results obtained using the N-layer model and the ray approach. The additional advantages of oxide layer, apart from sensitivity enhancement, are protection of metallic layer from oxidation, tunability of the resonance wavelength region, biocompatibility and capability of gas sensing.

Journal ArticleDOI
TL;DR: In this paper, the authors reported that 0.05% H 2 gas at room temperature can be detected using acids functionalized multiwalled carbon nanotubes (F-MWCNTs).
Abstract: Carbon nanotubes (CNTs) are extremely sensitive to environmental gases. Detection of H 2 gas at room temperature with fast response and recovery time is still a challenge. Here, we report that 0.05% H 2 gas at room temperature can be detected using acids functionalized multiwalled carbon nanotubes (F-MWCNTs). F-MWCNTs showed faster response to H 2 gas as compared to pristine multiwalled carbon nanotubes (P-MWCNTs). The effect of functionalization on the P-MWCNTs structure and their electrical properties are investigated using different techniques. The calculated crystallite size of the acids treated nanotubes from the Raman spectra is found to decrease to 14.6 nm as compared to 15.2 nm for the pristine. Also, due to attchements of functional groups on the nanotubes, the interplanar size of F-MWCNTs is increased, as identified from high resolution transmission electron microscopy (HR-TEM) and the X-ray diffraction (XRD) analysis. The presence of functional groups at the nanotubes walls after acids treatments is confirmed by fourier transform infrared (FTIR) spectra. Furthermore, the current carrying capacity of F-MWCNTs is found to increase to 35 mA from 49 μA at low sweep voltage. It is also observed that, the recovery time of F-MWCNTs sensor decreases to 100 s for 0.05% of H 2 gas as compared to 190 s for the P-MWCNTs.

Journal ArticleDOI
TL;DR: In this article, the core and cladding of a waveguide are formed by polydimethylsiloxane (PDMS) and the refractive index difference is realized by controlling the mixing ratio of base and curing agent.
Abstract: We report on a novel fabrication technology for building a waveguide system with its core and cladding both formed by Polydimethylsiloxane (PDMS). The refractive index difference is realized by controlling the mixing ratio of base and curing agent. The entire process only requires regular PDMS material and is completely compatible with soft lithography process. The experimental results show a good confinement of light and the transmission loss was about 1.1 dB/cm at 460 nm.

Journal ArticleDOI
TL;DR: In this article, the poling and characteristics of a melt-spun piezoelectric bicomponent fiber with poly(vinylidene fluoride) (PVDF) as its sheath component and a conductive composite with car...
Abstract: This study reports on the poling and characteristics of a melt-spun piezoelectric bicomponent fiber with poly(vinylidene fluoride) (PVDF) as its sheath component and a conductive composite with car ...

Journal ArticleDOI
TL;DR: This work reports on the evaluation of a WSN deployed in a real operational boiler facility and evaluates the catalytic sensor response under various conditions.
Abstract: Wireless sensor networks (WSN) have been adopted in various monitoring applications. However, due to the high power consumption of catalytic gas sensors, which enable reliable gas detection, there is a lack of real WSN deployments aimed at the monitoring of combustible gases. This work reports on the evaluation of a WSN deployed in a real operational boiler facility. The WSN consists of nine battery-powered wireless sensor nodes (with an onboard catalytic sensor) controlled by a network coordinator. In this safety critical environment our objective is twofold: (i) guarantee precise and fast sensor response, and (ii) deliver the sensed data from the sensor nodes to the network coordinator safely in case of methane leakage. We first describe the deployment of the WSN and then evaluate the catalytic sensor response under various conditions. Besides, we evaluate the wireless links using the received signal strength indicator (RSSI) and link quality indicator (LQI) metrics. Finally, the experimental results demonstrate that during 5 months of deployment the sensor nodes have been discharged for 22–27%.

Journal ArticleDOI
TL;DR: In this article, a micro electro mechanical system (MEMS) air-microfluidic particulate matter (PM) sensor is proposed for continuous recording of personal PM exposure levels.
Abstract: We present the design and fabrication of a micro electro mechanical systems (MEMS) air-microfluidic particulate matter (PM) sensor, and show experimental results obtained from exposing the sensor to concentrations of tobacco smoke and diesel exhaust, two commonly occurring PM sources. Our sensor measures only 25 mm × 21 mm × 2 mm in size and is two orders of magnitude smaller than commercially available direct mass PM sensors. The small shape allows our sensor to be used for continuous recording of personal PM exposure levels. The sensor contains an air-microfluidic circuit that separates the particles by size (virtual impactor) and then transports and deposits the selected particles using thermophoretic precipitation onto the surface of a microfabricated mass-sensitive film bulk acoustic resonator (FBAR). The mass-loading of the FBAR causes a change in its resonant frequency, and the rate of the frequency change corresponds to the particle concentration in the sampled air volume. We present experimental results that demonstrate the performance of our sensor for measuring PM mass emitted from diesel exhaust and tobacco smoke, and show that it exhibits sensitivity approaching 2 μg/m3 with up to 10 min integration time.

Journal ArticleDOI
TL;DR: In this article, a mode degeneration method is adopted that converts the longitudinal response excited by the axially poled piezoceramic discs in the transducer into combined longitudinal and torsional vibration in the front mass using geometric modifications of the wave path.
Abstract: This study investigates combining longitudinal and torsional (L–T) vibration responses at the output face of a Langevin transducer. A mode degeneration method is adopted that converts the longitudinal response excited by the axially poled piezoceramic discs in the transducer into combined L–T vibration in the transducer front mass using geometric modifications of the wave path. The study uses three techniques; numerical, analytical, and experimental, in order to estimate and validate transducer electro-mechanical parameters for different geometric modifications, and also to evaluate transducer performance for different excitation levels in terms of the desired L–T response. A finite element (FE) analysis is used to optimise the mechanical structure of the transducer while the analytical model, which is based on an equivalent-circuit approach, is used to estimate the electrical impedance spectra and to confirm some of the FE calculations prior to fabrication. These models are then validated through an experimental characterization of the vibration response and impedance response and the results show that the operating frequency and torsionality can be tailored through modification of the transducer geometry.

Journal ArticleDOI
TL;DR: In this article, the authors proposed a self-temperature compensation method for eddy-current sensors (ECSs) to reduce the thermal drift of ECSs by two orders of magnitude.
Abstract: This paper proposes a new method to reduce the thermal drift of eddy-current sensors (ECSs) by two orders of magnitude. Theoretical analysis shows that a well-designed bridge will help to decouple two vectors related to the resistance and inductance variations of the sensing coil of ECSs. Experiments show resistance variation has a considerably larger coefficient with temperature change compared to that of inductance variation. Other than being neglected, resistance variation compensates for the influence of temperature on inductance variation, which is used to derive true displacement information. A prototype ECS with high-resolution of sub-nanometer and ultrahigh thermal stability is manufactured and tested. Results show that the thermal drift of the prototype ECS is approximately 2.6 nm/°C, equivalent to 9.7 ppm/°C of the coil's inductance change. This self-temperature compensation method for ECS is simple, low cost, universal, very effective, and has competitive advantages in most applications.

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a double nonlinear bi-stable oscillator with a large amplitude response over a broad range of frequencies, which only gives a suitable response if the dominant ambient vibration frequency is tuned to the mechanical resonance.
Abstract: In this paper a new strategy for developing broadband, bi-directional, vibration energy harvesters is presented. Often energy harvesting systems address unidirectional incoming energy, however this is a strong limitation when considering real applications; in fact it is very likely that incoming vibrations will not be aligned with the direction of motion of the harvester. Therefore the presence of irregular vibrations along several orientations reduces the energy conversion and the harvester efficiency. Furthermore, often the ambient vibrations come with energy distributed over a wide spectrum of frequencies, with predominance of low frequency components such as vibration generated by: highway traffic, human motions, trains, electrical machines and generic noise-induced vibrations. The classical approach is based on vibrating mechanical bodies (linear systems) able to collect energy through the adoption of smart materials, magnetic or electrostatic solutions. Moreover this family of systems performs poorly for off-resonance conditions. For this reasons suitable harvester architecture for collecting energy from vibrations having a broad spectrum and distributed along different directions is needed. This work addresses both these issues by proposing a double nonlinear bi-stable oscillator with a large amplitude response over a broad range of frequencies. Such system improves traditional scavengers based on linear mechanical principles, which only give a suitable response if the dominant ambient vibration frequency is tuned to the mechanical resonance. Moreover a suitable topology of the double bistable oscillator is proposed such to obtain a bi-axial vibrations energy harvester. The system proposed here is composed of two magnetically coupled bi-stable beams, having orthogonal directions of deflection, with piezoelectric output; in presence of mechanical vibrations the beams will respond to both the inertial excitation and the magnetic coupling. Therefore the total output power, being the sum of the two piezoelectric outputs, will be optimized independently of the direction of the incoming vibrations. In this paper the two dimensional wide-band energy harvester is first described and analytically modeled, extensive simulations have been performed to evaluate the behavior of the two magnetically coupled beams. A macro-prototype has been conceived and realized and a measurement campaign has been performed in order to validate the principle.

Journal ArticleDOI
TL;DR: In this article, the authors proposed a decoupled XY stage for micro/nano positioning and manipulation applications, where two piezoelectric actuators generate motions, and the cross-axis couplings are attenuated by statically indeterminate symmetric (SIS) structures.
Abstract: This paper presents fundamental issues in establishing a decoupled XY stage for micro/nano positioning and manipulation applications. In the proposed XY stage, two piezoelectric actuators (PEAs) generate motions, and the cross-axis couplings are attenuated by statically indeterminate symmetric (SIS) structures. In static and dynamics modeling, the PEA can be treated as a force generator with a built-in spring-damper component. Subsequently, the driving force of the PEA is characterized as the input into the system, which removes the PEA's nonlinearities out of the linear dynamics of the stage. The influence of the contact interface between the PEA and the stage is analytically investigated. For the proposed XY stage, the hysteresis of the PEA is compensated by cascading an inverse Prandtl-Ishlinskii (PI) model as a feedforward hysteresis compensator. A feedforward–feedback compound controller is also established to improve the tracking performance. Experimental results demonstrate that the tracking error can be reduced to the noise level on tracking 1-Degree-Of-Freedom (1-DOF) trajectories at low frequencies; for 2-DOF trajectories, the tracking error is influenced by the cross-axis couplings and the cooperative tracking performance between axes.

Journal ArticleDOI
TL;DR: In this paper, a multi-frequency vibration-based MEMS electromagnetic energy harvesting (EH) device was presented, fabricated and characterized, which consists of a permanent magnet and a circular suspension structure on a MEMS EH chip.
Abstract: A multi-frequency vibration-based MEMS electromagnetic energy harvesting (EH) device has been presented, fabricated and characterized in this paper. It consists of a permanent magnet and a circular suspension structure on a MEMS EH chip. By emulating the magnetic field of a cylinder magnet, the gap distance between the magnet and EH chip is optimized to be zero for achieving larger magnetic flux change and higher output performance. From the experimental results, the vibration energy can be harvested at three excitation frequencies of 840, 1070 and 1490 Hz, which corresponds to the out-of-plane (mode I), torsion (mode II/III) and in-plane (mode IV/V) vibrations of the EH device, respectively. The maximum power densities at these three frequencies are 0.157, 0.014 and 0.117 μW/cm 3 , respectively, for a matched load resistance of 626 Ω and an input acceleration of 1.0 g. The feasibility study results show promising application potentials for harvesting energy from vibrations of multi-frequency.

Journal ArticleDOI
TL;DR: In this paper, a simple optical fiber structure with a section of no-core fiber for measuring relative humidity (RH) is presented, where Moisture-sensitive materials HEC/PVDF are used to form the hydrogel coating on the nocore fiber by dip impregnation method.
Abstract: A novel and simple optical fiber structure with a section of no-core fiber for measuring relative humidity (RH) is presented. Moisture-sensitive materials HEC/PVDF are used to form the hydrogel coating on the no-core fiber by dip impregnation method. Under different humidity conditions, the humidity induced refractive index changes on the outside coating of no-core fiber will lead to the variations of the optical output power. The different lengths of no-core fiber are tested at the two wavelengths of 1310 nm and 1550 nm, respectively. The results show that the structure with 2 cm no-core fiber has a higher RH sensitivity of 0.196 dB/%RH at 1310 nm and a better linearly response when the RH is lower than 75%. Furthermore, the optical output powers are measured with the rise and drop of RH, and the four times repetition are also recorded, which all demonstrate the good stability and repeatability of our proposed structure.

Journal ArticleDOI
TL;DR: A capacitive wearable contact lens sensor for monitoring of the IOP is developed and can be used for continuous IOP monitoring in clinics and at home for determination of the peak IOP for use in glaucoma diagnosis and monitoring.
Abstract: Intraocular pressure (IOP) is a primary indicative factor in the diagnosis and treatment monitoring of glaucoma. Measurement of IOP during conventional single office consultation is insufficient for determination of the pressure peak, and IOP profile is needed for peak determination. A capacitive wearable contact lens sensor for monitoring of the IOP is developed in this study. A curvature-sensitive inductor–capacitor sensor is fabricated and embedded inside a silicone rubber contact lens, such that the curvature of the lens is correlated with the resonance frequency of the sensor. The curvature of the lens is mechanically related to the IOP in the underlying eye such that the IOP can be determined from the resonance frequency of the sensor. To fit human eyes, the sensor was designed to have an outer diameter of 14 mm, radius of curvature of 8.5 mm, and operates in human IOP range between 5 and 40 mmHg. The frequency responses and the ability of the sensor to track IOP cycles were tested. Tests on model silicone eyes and enucleated porcine eyes showed that the sensors have a linearity R > 0.997 and a sensitivity >200 ppm/mmHg for IOP monitoring. Together with wireless reading circuitry taped around the eye socket, the new contact lens sensor can be used for continuous IOP monitoring in clinics and at home for determination of the peak IOP for use in glaucoma diagnosis and monitoring.

Journal ArticleDOI
TL;DR: In this article, an electromagnetic energy harvester (EMEH) based on a multi-pole magnet to harvest energy from ambient vibrations is presented, which consists of a cylindrical housing made of acrylic glass, a copper coil, and NdFeB (N35) permanent magnets.
Abstract: This paper presents an electromagnetic energy harvester (EMEH) based on multi-pole magnet to harvest energy from ambient vibrations. The EMEH consists of a cylindrical housing made of acrylic glass, a copper coil, and NdFeB (N35) permanent magnets. The physical modeling of the EMEH has been demonstrated through a series of mathematical equations. MATLAB program has been used to calculate the open circuit voltages for different magnets. The finite element analysis (FEA) has been adopted to examine the magnetic field area and flux lines of the magnet encompassing the coil. The fabricated EMEH using 3 magnets can generate up to 4.84 mW with normalized power density (NPD) of 2.14 × 10 3 μW/g 2 cm 3 at a resonance frequency of 6 Hz against a load resistance of 1.0 kΩ.

Journal ArticleDOI
TL;DR: In this article, an AlN/free-standing nanocrystalline diamond (NCD) system is proposed in order to process high frequency surface acoustic wave (SAW) resonators for sensing applications.
Abstract: In this paper, an AlN/free-standing nanocrystalline diamond (NCD) system is proposed in order to process high frequency surface acoustic wave (SAW) resonators for sensing applications. The main problem of synthetic diamond is its high surface roughness that worsens the sputtered AlN quality and hence the device response. In order to study the feasibility of this structure, AlN films from 150 nm up to 1200 nm thick have been deposited on free-standing NCD. We have then analysed the influence of the AlN layer thickness on its crystal quality and device response. Optimized thin films of 300 nm have been used to fabricate of one-port SAW resonators operating in the 10–14 GHz frequency range. A SAW based sensor pressure with a sensibility of 0.33 MHz/bar has been fabricated.

Journal ArticleDOI
TL;DR: In this article, a micro-sized MFC having optimal biofilm formation and minimal oxygen invasion into its anode chamber to generate high power density was reported. And the maximum power density of the MFC was 95μW/cm 2, the highest value among previously reported micro-size MFCs and even comparable to that of macro-scale counterparts.
Abstract: Microbial fuel cells (MFCs) represent an emerging technology for generating electricity from renewable biomass. Micro-sized MFCs show promising applications in certain niche applications. However, existing micro-sized MFCs are generally limited by their low power density, rendering them insufficient for practical applications. Here, we report a micro-sized MFC having optimal biofilm formation and minimal oxygen invasion into its anode chamber to generate high power density. The biofilm formed by exoelectrogen, Geobacter sulfurreducens , was studied by using four different thicknesses of photo-definable polydimethylsiloxane (PDMS) spacer; 10, 20, 55, and 155 μm. Both current and power densities were significantly limited when the PDMS spacer was less than 55 μm thick. The maximum power density of our MFC was 95 μW/cm 2 , the highest value among previously reported micro-sized MFCs and even comparable to that of macro-scale counterparts.

Journal ArticleDOI
TL;DR: In this paper, a mechanically compliant tactile sensor has been developed through direct-write deposition of a flexible conductive nanocomposite embedded between flexible polyurethane materials, which can detect applied forces at distinct locations on the surface.
Abstract: A mechanically compliant tactile sensor has been developed through direct-write (DW) deposition of a flexible conductive nanocomposite embedded between flexible polyurethane materials. Dispersion of multi-walled carbon nanotubes (MWCNTs) in a flexible and photocurable monomer introduced electrical and piezoresistive properties to the polymer which was used for the flexible conductive nanocomposite. Dispensing experiments were performed using the developed DW system to precisely create and embed the sensor elements between polyurethane substrates. From the experimental results, several flexible sensors including highly stretchable sensor elements (wires) were fabricated. Experiments were also performed to show that the sensor could detect applied forces at distinct locations on the surface. Slip was detected by examining the frequency content of the signals; sliding contact was characterized by a greater presence of high frequency power spectral density caused by mechanical vibrations that occur during slip. A Chebyshev band pass filter was developed to amplify these vibrations to distinguish between slip and nonslip tactile events. Finally, it is concluded that the study demonstrated in this work provides compelling evidence that the suggested materials, and methods of fabrication and characterization are promising for compliant tactile sensors.

Journal ArticleDOI
TL;DR: In this paper, undoped and Sn-doped ZnO nanopowder samples were prepared by the sol-gel method and the crystalline structure and surface morphology of the samples were analyzed by X-ray diffraction and atomic force microscopy.
Abstract: Undoped and Sn-doped ZnO nanopowder samples were prepared by the sol–gel method. The crystalline structure and surface morphology of the samples were analyzed by X-ray diffraction and atomic force microscopy. X-ray diffraction results indicate that the samples exhibit a hexagonal crystal structure. Electrical properties of the samples were measured by two probe method. The activation energies of the ZnO samples for low and high temperatures regions were determined. The optical band gaps of the samples were determined by optical absorption method. It was found that the samples have a direct transition optical band gap and the optical band gap values of the ZnO samples were changed with Sn doping. Quartz crystalline microbalance (QCM) technique was employed to investigate sensor features of the ZnO samples. The humidity sensor properties of undoped and Sn-doped ZnO samples based on quartz crystalline microbalance sensors were investigated. The obtained results indicate that the undoped and Sn-doped ZnO nanopowder samples can be used for humidity sensor applications.

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TL;DR: In this paper, a triaxial tactile sensor using piezoresistive beams is presented, which is composed of two pairs of sidewall-doped Si beams for shear stress sensing and one pair of surface-Doped Si beam for normal stress sensing.
Abstract: This paper reports on a triaxial tactile sensor using piezoresistive beams. The sensor chip is composed of two pairs of sidewall-doped Si beams for shear stress sensing and one pair of surface-doped Si beams for normal stress sensing. The sizes of the shear- and pressure-sensing beams are 180 μm × 15 μm × 20 μm and 250 μm × 50 μm × 20 μm (length × width × thickness), respectively. The sensor chip is embedded in a PDMS sheet 10 mm × 10 mm × 2 mm in size. Because the simple beam structure can be fabricated easily, the proposed sensor is compatible with semiconductor device fabrication. The fabricated sensor was evaluated for normal and shear stress (0–400 kPa and 0–100 kPa, respectively). The responses of the corresponding beam pairs were found to be proportional to the magnitude of the applied stresses without the influence of the other stresses. The relationship between the angle of shear stress and the responses of each beam pair was also evaluated. Each beam pair detects only one axis's shear stress and showed little reaction to the other axes’ shear stress. As a result, the proposed sensor can measure the three axial components of normal and shear stress independently.